Driving circuit and display device

ABSTRACT

A display device includes a plurality of gate lines; a plurality of data lines; a plurality of pixel electrodes electrically connected with the plurality of data lines; a plurality of common electrodes corresponding to two or more pixel electrodes among the plurality of pixel electrodes; a data driving circuit outputting data voltages to the plurality of data lines; and a driving circuit outputting a first driving signal with a first voltage level to at least one common electrode among the plurality of common electrodes during a first driving period and a second driving signal with a second voltage level and a third voltage level to the at least one common electrode during a second driving period, the second driving signal being a pulse signal, wherein the second voltage level and the third voltage level differ from the first voltage level.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/931,401, filed May 13, 2020, which claims priority from Korean PatentApplication No. 10-2019-0073354, filed on Jun. 20, 2019, which arehereby incorporated by reference in their entirety for all purposes asif fully set forth herein.

BACKGROUND Field of the Disclosure

The present disclosure relates to a driving circuit and a displaydevice.

Description of the Background

The growth of the intelligent society leads to increased demand forimage display devices and use of various types of display devices, suchas liquid crystal displays, organic light emitting displays, etc.

The display device recognizes the user's touch on the display panel andperforms input processing based on the recognized touch so as to providemore various functions to the user.

An example display device capable of touch recognition may apply touchdriving signals to multiple touch electrodes arranged or embedded in thedisplay panel, sense a variation in capacitance caused by the user'stouch, and detect whether there is a touch and, if so, the coordinatesof the touch.

The touch electrodes may be arranged on the display panel and havedisplay driving voltages applied thereto. As a touch driving signal isapplied to the display driving electrodes, display driving may be notenabled during the period of sensing the touch or image qualityabnormality may occur.

SUMMARY

The present disclosure provides a driving circuit and display device,which use an electrode for display driving as a touch electrode and arecapable of performing touch sensing simultaneously with display driving.

The present disclosure provides a driving circuit and display device,which may prevent image quality abnormality due to application of asignal for touch driving to the display driving electrode.

According to various aspects of the disclosure, a display devicecomprises a plurality of gate lines, a plurality of data lines, aplurality of pixel electrodes electrically connected with the datalines, a plurality of common electrodes corresponding to two or morepixel electrodes among the plurality of pixel electrodes, a data drivingcircuit outputting data voltages to the plurality of data lines, and adriving circuit outputting a first driving signal with a first voltagelevel to at least one common electrode of the plurality of commonelectrodes in a first driving period and a second driving signal with asecond voltage level and a third voltage level to the at least onecommon electrode in a second driving period, the second driving signalbeing a pulse signal. The second voltage level and the third voltagelevel differ from the first voltage level.

Here, the first voltage level may be higher than the second voltagelevel and lower than the third voltage level.

Or, the first voltage level may be lower than the second voltage level,and the second voltage level may be lower than the third voltage level.

Thus, when the data voltage corresponding to the same grayscale in thefirst driving period and second driving period is supplied, thedifference between the data voltage and the voltage applied to thecommon electrode in the first driving period may differ from thedifference between the data voltage and the voltage applied to thecommon electrode in the second driving period.

According to various aspects of the disclosure, a driving circuitcomprises an electrode driver outputting a first driving signal with afirst voltage level to at least one common electrode of a plurality ofcommon electrodes embedded in a panel in a first driving period and asecond driving signal with a second voltage level and a third voltagelevel to the at least one common electrode in a second driving period,the second driving signal being a pulse signal, and the electrode driverreceiving a sensing signal from at least one common electrode to whichthe second driving signal has been applied in the second driving periodand a sensing signal converter outputting sensing data into which thesensing signal received in the second driving period has been converted.The second voltage level and the third voltage level differ from thefirst voltage level.

According to various aspects of the disclosure, touch sensing anddisplay driving may simultaneously be performed by supplying the datavoltage modulated based on the touch driving signal in the period duringwhich the touch driving signal is applied to the common electrode.

According to various aspects of the disclosure, the level of the voltageapplied to the common electrode in the period during which no touchdriving signal is applied may be set to differ from the voltage level ofthe touch driving signal, thereby preventing an image qualityabnormality from occurring in the touch driving signal-applied period.

DESCRIPTION OF DRAWINGS

The above and features, and advantages of the present disclosure will bemore clearly understood from the following detailed description, takenin conjunction with the accompanying drawings, in which:

FIG. 1 is a view schematically illustrating a configuration of a displaydevice according to the present disclosure;

FIG. 2 is a view illustrating an example of timing of display drivingand touch sensing of a display device according to the presentdisclosure;

FIG. 3 is a view illustrating another example of timing of displaydriving and touch sensing of a display device according to the presentdisclosure;

FIG. 4 is a view illustrating various examples of timing of fingersensing and pen sensing according to the display driving and touchsensing timings shown in FIG. 3;

FIG. 5 is a view illustrating an example of image quality abnormalitydue to signals applied to a common electrode during a period when touchsensing is performed and a period when touch sensing is not performed ina display device according to the present disclosure;

FIG. 6 is a view illustrating example signals applied to a commonelectrode during a period when touch sensing is performed and a periodwhen touch sensing is not performed in a display device according to thepresent disclosure;

FIG. 7 is a view illustrating other example signals applied to a commonelectrode during a period when touch sensing is performed and a periodwhen touch sensing is not performed in a display device according to thepresent disclosure;

FIG. 8 is a view illustrating an example difference between commonvoltage and data voltage, caused by signals applied to a commonelectrode during a period when touch sensing is performed and a periodwhen touch sensing is not performed in a display device according to thepresent disclosure;

FIG. 9 is a view illustrating an example in which image quality isenhanced when a signal is applied to a common electrode according to theexamples shown in FIGS. 6 to 8; and

FIG. 10 is a view illustrating an example configuration of a powercircuit and a touch driving circuit for outputting signals to a commonelectrode in a display device according to the present disclosure.

DETAILED DESCRIPTION

In the following description of examples or aspects of the disclosure,reference will be made to the accompanying drawings in which it is shownby way of illustration specific examples or aspects that can beimplemented, and in which the same reference numerals and signs can beused to designate the same or like components even when they are shownin different accompanying drawings from one another. Further, in thefollowing description of examples or aspects of the disclosure, detaileddescriptions of well-known functions and components incorporated hereinwill be omitted when it is determined that the description may make thesubject matter in some aspects of the disclosure rather unclear. Theterms such as “including”, “having”, “containing”, “constituting” “makeup of”, and “formed of” used herein are generally intended to allowother components to be added unless the terms are used with the term“only”. As used herein, singular forms are intended to include pluralforms unless the context clearly indicates otherwise.

Terms, such as “first”, “second”, “A”, “B”, “(A)”, or “(B)” may be usedherein to describe elements of the disclosure. Each of these terms isnot used to define essence, order, sequence, or number of elements etc.,but is used merely to distinguish the corresponding element from otherelements.

When it is mentioned that a first element “is connected or coupled to”,“contacts or overlaps” etc. a second element, it should be interpretedthat, not only can the first element “be directly connected or coupledto” or “directly contact or overlap” the second element, but a thirdelement can also be “interposed” between the first and second elements,or the first and second elements can “be connected or coupled to”,“contact or overlap”, etc. each other via a fourth element. Here, thesecond element may be included in at least one of two or more elementsthat “are connected or coupled to”, “contact or overlap”, etc. eachother.

When time relative terms, such as “after,” “subsequent to,” “next,”“before,” and the like, are used to describe processes or operations ofelements or configurations, or flows or steps in operating, processing,manufacturing methods, these terms may be used to describenon-consecutive or non-sequential processes or operations unless theterm “directly” or “immediately” is used together.

In addition, when any dimensions, relative sizes etc. are mentioned, itshould be considered that numerical values for an elements or features,or corresponding information (e.g., level, range, etc.) include atolerance or error range that may be caused by various factors (e.g.,process factors, internal or external impact, noise, etc.) even when arelevant description is not specified. Further, the term “may” fullyencompasses all the meanings of the term “can”.

FIG. 1 is a view schematically illustrating a configuration of a displaydevice 100 according to various aspects of the disclosure.

Referring to FIG. 1, according to various aspects of the disclosure, adisplay device 100 may include a display panel 110, a gate drivingcircuit 120, a data driving circuit 130, and a controller 140. Thedisplay device 100 may include a touch driving circuit 150 for sensing atouch on the display panel 110 and a touch controller 160.

The display panel 110 may include a plurality of gate lines GL, aplurality of data lines DL, and multiple subpixels SP at the crossingsof the gate lines GL and the data lines DL. A pixel electrode PXL may bedisposed in each subpixel SP.

Multiple touch electrodes TE may be arranged or embedded in the displaypanel 110, and multiple touch lines TL for electrically connecting thetouch electrodes TE with the touch driving circuit 150 may be arrangedon the display panel 110.

A configuration for display driving in the display device 100 isdescribed first. The gate driving circuit 120 controls the drivingtiming of the subpixels SP arranged in the display panel 110. The datadriving circuit 130 supplies data voltage Vdata corresponding to imagedata to the subpixels SP to allow the subpixels SP to represent abrightness corresponding to the grayscale of the image data, therebydisplaying an image.

Specifically, the gate driving circuit 120 may be controlled by thecontroller 140 to sequentially output scan signals to the plurality ofgate lines GL disposed in the display panel 110, controlling the drivingtiming of the subpixels SP.

The gate driving circuit 120 may include one or more gate driverintegrated circuits (GDICs). Depending on driving schemes, the gatedriving circuit 120 may be positioned on only one side, or each of twoopposite sides, of the display panel 110.

Each gate driver integrated circuit (GDIC) may be connected to thebonding pad of the display panel 110 in a tape automated bonding (TAB)or chip-on-glass (COG) scheme or may be implemented in a gate-in-panel(GIP) type to be directly disposed in the display panel 110 or, in somecases, may be integrated in the display panel 110. Each gate driverintegrated circuit (GDIC) may also be implemented in a chip-on-film(COF) scheme to be mounted on a film connected to the display panel 110.

The data driving circuit 130 receives image data (or input data) fromthe controller 140 and converts the image data into an analog datavoltage. The data driving circuit 130 outputs a data voltage to eachdata line DL according to the timing of applying a scan signal via thegate line GL, allowing each subpixel SP to represent a brightnessaccording to the image data.

The data driving circuit 130 may include one or more source driverintegrated circuits (SDICs).

Each source driver integrated circuit (SDIC) may include, e.g., shiftregisters, latch circuits, digital-analog converters, and outputbuffers.

Each source driver integrated circuit (SDIC) may be connected to thebonding pad of the display panel 110 in a TAB or COG scheme or may bedirectly disposed in the display panel 110 or, in some cases, may beintegrated in the display panel 110. Each source driver integratedcircuit (SDIC) may be implemented in a COF scheme in which case eachsource driver integrated circuit (SDIC) may be mounted on a filmconnected to the display panel 110 and be electrically connected withthe display panel 110 via wires on the film.

The controller 140 supplies various control signals to the gate drivingcircuit 120 and the data driving circuit 130 and controls the operationof the gate driving circuit 120 and the data driving circuit 130.

The controller 140 enables the gate driving circuit 120 to output scansignals according to the timing of implementing each frame, convertsimage data received from the outside to meet the data signal format usedby the data driving circuit 130, and outputs the resultant image data tothe data driving circuit 130.

The controller 140 receives, from the outside (e.g., a host system),various timing signals including a vertical synchronization signalVSYNC, a horizontal synchronization signal HSYNC, an input data enablesignal DE, and a clock signal, along with the image data.

The controller 140 may generate a diversity of control signals using thetiming signals received from the outside and output the control signalsto the gate driving circuit 120 and the data driving circuit 130.

As an example, to control the gate driving circuit 120, the controller140 outputs various gate control signals GCS including a gate startpulse GSP, a gate shift clock GSC, and a gate output enable signal GOE.

The gate start pulse GSP controls the operation start timing of one ormore gate driver integrated circuits GDICs constituting the gate drivingcircuit 120. The gate shift clock GSC is a clock signal commonly inputto one or more gate driver integrated circuits GDICs and controls theshift timing of the scan signals. The gate output enable signal GOEdesignates timing information about one or more gate driver integratedcircuits GDICs.

To control the data driving circuit 130, the controller 140 outputsvarious data control signals DCS including, e.g., a source start pulseSSP, a source sampling clock SSC, and a source output enable signal SOE.

The source start pulse SSP controls the data sampling start timing ofone or more source driver integrated circuits SDICs constituting thedata driving circuit 130. The source sampling clock SSC is a clocksignal for controlling the sampling timing of data in each source driverintegrated circuit (SDIC). The source output enable signal SOE controlsthe output timing of the data driving circuit 130.

The display device 100 may further include a power management integratedcircuit (not shown) that supplies various voltages or currents to, e.g.,the display panel 110, the gate driving circuit 120, the data drivingcircuit 150, and the touch driving circuit 150 or controls variousvoltages or currents to be supplied.

Each subpixel SP may be defined by the crossing of the gate line GL andthe data line DL, and liquid crystals or a light emitting element may bedisposed in each subpixel SP depending on the type of the display device100.

As an example, when the display device 100 is a liquid crystal displaydevice, the display device 100 may include a light source device, suchas a backlight unit, to emit light to the display panel 110. Liquidcrystals are disposed in the subpixel SP of the display panel 110. Thealignment of liquid crystals may be adjusted by an electric fieldcreated as data voltage (Vdata) is applied to each subpixel SP, therebyrepresenting a brightness per image data and displaying an image.

As an example, when the display device 100 is an organic light emittingdisplay device, an organic light emitting diode (OLED) is disposed ineach subpixel SP, and the current flowing to the OLED per data voltagesupplied to the subpixel SP may be controlled to represent a brightnessper image data supplied to the subpixel SP.

Or, in some cases, a light emitting diode (LED) may be disposed in eachsubpixel SP to display images.

Meanwhile, according to various aspects of the disclosure, the displaydevice 100 may detect the user's touch on the display panel 110 usingthe touch driving circuit 150 and the touch electrodes TE included inthe display panel 110.

As an example, the display panel 110 may include the plurality of touchelectrodes (TE) and a plurality of touch lines (TL) to connect the touchelectrodes TE with the touch driving circuit 150.

The touch electrodes TE may be disposed on, or embedded in, the displaypanel 110.

The touch electrodes TE may be electrodes used for display driving or beseparate electrodes provided for touch sensing. The touch electrode TEmay be a whole transparent electrode with no open area or an opaquemesh-shaped electrode. The touch electrode TE may be a transparentelectrode partially having an open area.

As an example, when the display device 100 is a liquid crystal displaydevice, the touch electrode TE may be a common electrode COM embedded inthe display panel 110 and, upon display driving, having a common voltageVcom applied thereto.

In other words, separate common electrodes COM may be arranged on thedisplay panel 110 to be used as touch electrodes TE for touch sensing.Thus, each touch electrode TE may be disposed to overlap multiplesubpixels SP.

According to various aspects of the disclosure, although the displaydevice 100 is a liquid crystal display device, as an example, for easeof description, aspects of the disclosure are not limited thereto.

The touch electrodes TE may be electrically connected with the touchdriving circuit 150 via the touch lines TL arranged on the display panel110.

The touch driving circuit 150 may include an amplifier that outputs atouch driving signal TDS to the touch electrode TE and receives a touchsensing signal TSS from the touch electrode TE, an integrator thatintegrates output signals from the amplifier, and an analog-digitalconverter that converts the output signal from the integrator into adigital signal.

In some cases, the touch driving circuit 150 may be integrated with thedata driving circuit 130.

The touch driving circuit 150 may be connected with the touch electrodesTE in a one-to-one manner to receive the touch sensing signal TSS. Inother words, the touch driving circuit 150 may output the touch drivingsignal TDS to the touch electrode TE via the touch line TL, receive thetouch sensing signal TSS, and sense a variation in self capacitance dueto a touch.

The touch electrodes TE may be divided into driving electrodes andsensing electrodes, and the touch driving circuit 150 may connect toeach of the driving electrodes and the sensing electrodes. In such acase, the touch driving circuit 150 may output the touch driving signalTDS to the driving electrode, receive the touch sensing signal TSS fromthe sensing electrode, and sense a variation in mutual capacitancebetween the driving electrode and sensing electrode due to a touch.

The touch driving circuit 150 converts the received touch sensing signalTSS into digital sensing data and transmits the digital sensing data tothe touch controller 160.

The touch controller 160 may control the driving of the touch drivingcircuit 150, receive sensing data from the touch driving circuit 150,and detect the user's touch on the display panel 110 based on thereceived sensing data.

In other words, the touch controller 160 may detect a variation in selfcapacitance or mutual capacitance from the sensing data and detect,e.g., the presence or absence of a touch or the coordinates of a touchbased on the detected capacitance variation.

According to various aspects of the disclosure, the display device 100may perform touch sensing simultaneously with display driving, using thecommon electrodes COM as touch electrodes TE. In other words, touchsensing may be performed during the whole or part of the period whendisplay driving is performed.

FIG. 2 is a view illustrating an example of timing of display drivingand touch sensing of a display device 100 according to various aspectsof the disclosure.

Referring to FIG. 2, according to various aspects of the disclosure, thedisplay device 100 may perform touch sensing simultaneously with displaydriving.

Here, the touch sensing period may be identical to the display drivingperiod or may be a blank period within the display driving period. Inother words, touch sensing may be independently performed regardless ofdisplay driving and, thus, touch sensing may be performed simultaneouslywith display driving.

When touch sensing is performed simultaneously with display driving, thetouch driving signal TDS is applied to the touch electrode TE. Here, thetouch driving signal TDS may be a pulse signal whose voltage varies overtime. For display driving, data voltage Vdata may be supplied to thedata line DL, and a scan signal generated using a gate high voltage VGHand a gate low voltage VGL may be output to the gate line GL.

At this time, when the common electrode COM of the display panel 110 isused as the touch electrode TE, the touch driving signal TDS is appliedto the touch electrode TE. Thus, no voltage difference corresponding toimage data may be formed between the common electrode COM and the pixelelectrode PXL to which the data voltage Vdata is applied.

In other words, since the touch driving signal TDS is varied over time,no voltage difference corresponding to the image data is formed betweenthe pixel electrode PXL and the common electrode COM to which the touchdriving signal TDS is applied, so that the subpixel SP may not representthe brightness corresponding to the image data.

Thus, a voltage difference corresponding to the image data may be formedbetween the pixel electrode PXL and the touch driving signal(TDS)-applied common electrode COM by supplying modulated data voltageVdata to the data line DL based on the touch driving signal TDS.

As an example, the data voltage Vdata may be modulated based on thepulse width modulation signal PWM used for generating the touch drivingsignal TDS.

The modulation of the data voltage Vdata may be performed, e.g., in sucha manner as to modulate the gamma voltage used for generating the datavoltage Vdata in the data driving circuit 130. Or, the ground voltage ofthe display panel 110 may be modulated so that the modulated datavoltage Vdata may be supplied to the data line DL.

The gate low voltage VGL may be modulated based on the touch drivingsignal TDS, so that the modulated scan signal may be applied to the gateline GL, allowing the gate line GL to be normally driven.

As such, the data voltage Vdata applied to the data line DL and the scansignal applied to the gate line GL may be modulated based on the touchdriving signal TDS, allowing display driving and touch sensing to beperformed simultaneously.

According to various aspects of the disclosure, the display device 100may perform touch sensing simultaneously with display driving or mayperform touch sensing only during a portion of the display drivingperiod.

FIG. 3 is a view illustrating another example of timing of displaydriving and touch sensing of a display device 100 according to variousaspects of the disclosure.

Referring to FIG. 3, touch sensing may be performed within the displaydriving period.

Within the period during which display driving and touch sensing aresimultaneously performed, a touch driving signal TDS for touch sensingmay be applied to the common electrode COM, and data voltage Vdatamodulated based on the touch driving signal TDS may be supplied to thedata line DL. The scan signal modulated based on the touch drivingsignal TDS may be applied to the gate line GL.

This means that display driving and touch sensing are performedtemporally within the same time period but not that the display drivingarea and touch sensing area are the same. In other words, although themodulated common voltage Vcom is supplied to the overall display panel110 within the period during which display driving and touch sensing aresimultaneously performed in one frame, the area where the data voltageVdata is supplied and the area where the sensing signal is detected maynot overlap each other.

As such, the display device 100 may supply the modulated voltage to,e.g., the common electrode COM and data line DL, displaying an image onthe display panel 110 and performing touch sensing.

The display device 100 may perform display driving alone during someperiod within one frame.

In the period during which display driving only is performed, apredetermined level (e.g., 0V or 5.5V) of constant voltage, rather thanthe modulated voltage, may be applied to the common electrode COM.Further, non-modulated data voltage Vdata may be applied to the dataline DL, and a non-modulated scan signal may be applied to the gate lineGL. In other words, during the period when display driving alone isperformed, the data voltage Vdata for display driving alone may beapplied to the data line DL, and the gate voltage Vgate for displaydriving alone may be applied to the gate line GL.

Thus, even when touch sensing is performed simultaneously with displaydriving, a non-modulated constant voltage may be applied to the commonelectrode COM, and there may exist a period during which only displaydriving is performed. Further, in some cases, display driving and pentouch sensing may be performed within the period during which theconstant voltage is applied to the common electrode COM.

FIG. 4 is a view illustrating various example schemes of performingfinger sensing or pen sensing according to the timing of display drivingand touch sensing as shown in FIGS. 2 and 3.

Referring to FIG. 4, according to various aspects of the disclosure, thedisplay device 100 may perform display driving only and may performtouch sensing simultaneously with display driving. The display device100 may perform touch sensing only during a portion of the displaydriving period and may perform finger sensing (F/S) and pen sensing(P/S) during the same or different periods.

As an example, the display device 100 may perform only display drivingwithout touch sensing, e.g., finger sensing (F/S) and pen sensing (P/S),in one frame, e.g., the pth frame.

Or, the display device 100 may perform touch sensing, such as fingersensing (F/S) or pen sensing (P/S), during a portion, when touch sensingis needed, of the period when display driving is performed, e.g., theqth frame. Here, finger sensing (F/S) and pen sensing (P/S) may beperformed during non-overlapping periods.

Or, the display device 100 may perform touch sensing during the displaydriving period, e.g., the rth frame, and may perform finger sensing(F/S) and pen sensing (P/S) during overlapping periods. In such a case,the respective results of the finger sensing (F/S) and pen sensing (P/S)may be differentiated by signal analysis per sensing positions or analgorithm determined by the touch controller.

Without limitations thereto, display driving and touch sensing (fingersensing or pen sensing) may independently be performed at varioustimings.

As touch sensing is performed independently from display driving, asufficient touch sensing period may be secured, and the performance oftouch sensing may be enhanced.

In some cases, touch sensing may be performed during a portion of thedisplay driving period but not during another portion of the displaydriving period. In other words, touch sensing may be performed within arequired period regardless of display driving.

At this time, different signals may be applied to the common electrodeCOM, which is used as the touch electrode TE, in the period during whichtouch sensing is performed and the period during which no touch sensingis performed. Thus, a difference in image quality may occur between theperiod during which the touch driving signal TDS, a modulated signal, isapplied to the common electrode COM and the period during which anon-modulated common voltage Vcom is applied to the common electrodeCOM.

FIG. 5 is a view illustrating an example of image quality abnormalitydue to signals applied to a common electrode COM during a period whentouch sensing is performed and a period when touch sensing is notperformed in a display device 100 according to various aspects of thedisclosure.

Referring to FIG. 5, the first driving period P1 denotes a period duringwhich display driving is performed, but touch sensing is not, and thesecond driving period P2 denotes a period during which display drivingand touch sensing are performed simultaneously.

Since no touch sensing is performed in the first driving period P1, anon-modulated common voltage Vcom is applied to the common electrodeCOM. In the second driving period P2, a modulated touch driving signalTDS for touch sensing is applied to the common electrode COM. Further,in the second driving period P2, a modulated data voltage Vdata may besupplied to the pixel electrode PXL.

Here, as the voltage modulated based on the pulse width modulationsignal PWM is applied to the common electrode COM and pixel electrodePXL in the second driving period P2, the difference between the commonvoltage Vcom and the data voltage Vdata may be uneven.

As an example, although the common voltage Vcom and data voltage Vdataare modulated by the same pulse width modulation signal PWM, thedifference between the modulated common voltage Vcom and the modulateddata voltage Vdata may be uneven due to the difference in the supplysource of the pulse width modulation signal PWM. Further, the differencebetween the two voltages may be uneven due to a difference between theload according to an aspect the path of supplying the modulated commonvoltage Vcom and the load according to the path of supplying themodulated data voltage Vdata.

In such a case, an image quality abnormality may arise due to the unevendifference between the common voltage Vcom and data voltage Vdatasupplied for image displaying.

As an example, as shown in FIG. 5, when a start signal Vst indicatingthe start of one frame is applied, scan signals are sequentiallysupplied to the gate lines GL arranged on the display panel 110, anddisplay driving commences.

At this time, in the period, e.g., the first driving period P1, duringwhich no touch sensing is performed, a common voltage Vcom, which is anon-modulated constant voltage, is applied to the common electrode COM.In the period, e.g., the second driving period P2, during which touchsensing is performed, a touchscreen display TDS, which is a modulatedcommon voltage Vcom, may be applied to the common electrode COM.Further, a data voltage Vdata reflecting a variation in voltage due tothe voltage variation in the touch driving signal TDS applied to thecommon electrode COM is applied to the data line DL, and a scan signalreflecting a variation in voltage due to the voltage variation in thetouch driving signal TDS applied to the common electrode COM may beapplied to the gate line GL.

Here, as the modulated common voltage Vcom is applied, an image qualityabnormality may occur in the area where display driving is performed inthe period of applying the modulated common voltage Vcom.

Thus, in the period during which display driving is performed in area D1or D3 of the display panel 110, the constant common voltage Vcom may beapplied to the common electrode COM, preventing an image qualityabnormality from occurring. In contrast, as the modulated common voltageVcom and modulated data voltage Vdata are supplied in the period duringwhich display driving is performed in area D2, an image qualityabnormality may occur in area D2.

According to various aspects of the disclosure, there is provided a wayfor preventing a difference in image quality that arises in the periodduring which a modulated touch driving signal TDS is applied and in theperiod during which a non-modulated common voltage Vcom is applied in acase where touch sensing is performed during at least a portion of thedisplay driving period.

FIG. 6 is a view illustrating example signals applied to a commonelectrode COM during a period when touch sensing is performed and aperiod when touch sensing is not performed in a display device 100according to various aspects of the disclosure.

Referring to FIG. 6, the display device 100 may refrain from touchsensing like in the first driving period P1 among the periods duringwhich display driving is performed and may perform touch sensing like inthe second driving period P2.

Whether to perform touch sensing may be controlled by a touch syncsignal Tsync which may be a signal output from the touch controller 160.The touch sync signal Tsync may be a signal generated and output fromthe controller 140 which controls the timing of display driving andtouch sensing. Although FIG. 6 illustrates an example in which touchsensing is performed in a period during which the touch sync signalTsync is at a low level, touch sensing may be, in some case, performedin a period during which the touch sync signal Tsync is at a high level.

In the first driving period P1, a non-modulated constant common voltageVcom is applied to the common electrode COM. The data voltage Vdatasupplied to the data line DL and the scan signal supplied to the gateline GL may also be in a non-modulated form. Thus, the subpixel SP maybe charged with the data voltage Vdata, and display driving may beperformed.

In the second driving period P2, a touch driving signal TDS modulatedbased on a pulse width modulation signal is applied to the commonelectrode COM. Further, a data voltage Vdata modulated to correspond tothe touch driving signal TDS may be applied to the data line DL, and ascan signal modulated to correspond to the touch driving signal TDS maybe applied to the gate line GL.

Here, the voltage level of the common voltage Vcom applied to the commonelectrode COM in the first driving period P1 may be a first voltagelevel L1. The touch driving signal TDS applied to the common electrodeCOM in the second driving period P2 may be a pulse signal with a secondvoltage level L2 and a third voltage level L3.

At this time, the first voltage level L1 may differ from the secondvoltage level L2 and the third voltage level L3.

As an example, the first voltage level L1 may be lower than the secondvoltage level L2 and the third voltage level L3.

When the modulated voltage is applied to the common electrode COM andthe pixel electrode PXL, in the first driving period P1, the differencebetween the common voltage Vcom and the data voltage Vdata may be evenwhereas in the second driving period P2, the difference between thecommon voltage Vcom and the data voltage Vdata applied to the pixelelectrode PXL may be uneven due to application of the modulated voltageto the common electrode COM and the pixel electrode PXL.

In some cases, the peak where the difference between the common voltageVcom and the data voltage Vdata is positive (+) may be larger than thepeak where the difference between the common voltage Vcom and the datavoltage Vdata is negative (−).

In such a case, the voltage level of the common voltage Vcom applied tothe common electrode COM in the second driving period P2 may be allowedto be relatively higher than the voltage level of the common voltageVcom applied to the common electrode COM in the first driving period P1.

This may be regarded as raising the second voltage level L2 of the touchdriving signal TDS supplied in the second driving period P2 or aslowering the first voltage level L1 of the common voltage Vcom suppliedin the first driving period P1.

Raising the second voltage level 12 of the touch driving signal TDSsupplied in the second driving period P2 may render the root mean square(RMS) value of the differences between the common voltage Vcom and thedata voltage Vdata in the first driving period P1 and second drivingperiod P2 constant.

In other words, the difference between the common voltage Vcom and datavoltage Vdata in the first driving period P1 and the difference betweenthe common voltage Vcom and data voltage Vdata in the second drivingperiod P2 may be varied by altering the minimum voltage of the touchdriving signal TDS to the second voltage level L2 which is higher thanthe first voltage level L1 of the common voltage Vcom supplied in thefirst driving period P1 and driving the common electrode COM. The RMSvalue of the differences between the common voltage Vcom and datavoltage Vdata in the first driving period P1 and the RMS value of thedifferences between the common voltage Vcom and data voltage Vdata inthe second driving period P2 may be allowed to remain the same.

By so doing, the RMS value of the differences between the common voltageVcom and data voltage Vdata in the first driving period P1 and seconddriving period P2 may be adjusted to be even.

Further, when the grayscale represented by the data voltage Vdatasupplied in the first driving period P1 and second driving period P2 isconstant, the RMS value of the differences between the common voltageVcom and data voltage Vdata in the first driving period P1 and the RMSvalue of the differences between the common voltage Vcom and datavoltage Vdata in the second driving period P2 may be identical or berendered to fall within a predetermined range. Here, as the level of thecommon voltage Vcom supplied in the first driving period P1 and seconddriving period P2 is varied, the difference between the common voltageVcom and data voltage Vdata may be altered although the data voltageVdata representing the same grayscale is supplied in the first drivingperiod P1 and second driving period P2. In other words, even when thedifference between the common voltage Vcom and data voltage Vdata isvaried in the first driving period P1 and second driving period P2,image quality abnormality may be prevented by adjusting the RMS value ofthe differences between the common voltage Vcom and data voltage Vdatain each of the periods.

As such, a difference in image quality between the first driving periodP1 and second driving period P2 or an image quality abnormality in thesecond driving period P2 may be prevented from arising by settingdifferent levels of voltage applied to the common electrode COM in thefirst driving period P1 and second driving period P2.

In other words, the voltage level of the touch driving signal TDS may beset so that no image quality abnormality occurs in the second drivingperiod P2 during which the touch driving signal TDS modulated based onthe pulse width modulation signal PWM is applied to the common electrodeCOM. The set voltage level of the touch driving signal TDS may differfrom the voltage level of the common voltage Vcom applied to the commonelectrode COM in the first driving period P1.

In some cases, the first voltage level L1 of the common voltage Vcomapplied to the common electrode COM in the first driving period P1 maybe rendered to be higher than the second voltage level L2 of the touchdriving signal TDS applied to the common electrode COM in the seconddriving period P2.

FIG. 7 is a view illustrating other example signals applied to a commonelectrode COM during a period when touch sensing is performed and aperiod when touch sensing is not performed in a display device 100according to various aspects of the disclosure.

Referring to FIG. 7, a non-modulated common voltage Vcom may be appliedto the common electrode COM in a first driving period P1 among periodsduring which display driving is performed. Thus, non-modulated voltagesor signals may be applied to the data line DL and gate line GL.

In a second driving period P2, a touch driving signal TDS modulatedbased on a pulse width modulation signal PWM may be applied to thecommon electrode COM. Thus, a data voltage Vdata modulated to correspondto the touch driving signal TDS may be supplied to the data line DL. Ascan signal modulated to correspond to the touch driving signal may beapplied to the gate line GL.

Here, the common voltage Vcom applied to the common electrode COM in thefirst driving period P1 may have a first voltage level L1. The touchdriving signal TDS applied to the common electrode COM in the seconddriving period P2 may be a pulse signal with a second voltage level L2and a third voltage level L3.

In this case, the first voltage level L1 may be higher than the secondvoltage level L2 and lower than the third voltage level L3.

As an example, in the difference between the data voltage Vdata appliedto the pixel electrode PXL via the data line DL and the touch drivingsignal TDS, i.e., the common voltage Vcom, applied to the commonelectrode COM in the second driving period P2, the positive (+) peak maybe larger than the negative (−) peak as shown in FIG. 7.

In such a case, the difference between the data voltage Vdata and commonvoltage Vcom in the second driving period P2 may be varied by loweringthe second voltage level L2 of the touch driving signal TDS applied tothe common electrode COM in the second driving period P2. This may beregarded as raising the first voltage level L1 of the common voltageVcom applied to the common electrode COM in the first driving period P1.

As the voltage level of the touch driving signal TDS applied to thecommon electrode COM in the second driving period P2 is adjusted, theRMS value of the differences between the data voltage Vdata and thecommon voltage Vcom in the second driving period P2 may be adjusted tobe identical to the RMS value of the differences between the datavoltage Vdata and the common voltage Vcom in the first driving periodP1.

In other words, the RMS value of the differences between the datavoltage Vdata applied to the pixel electrode PXL and the common voltageVcom applied to the common electrode COM in the first driving period P1and second driving period P2 may be adjusted to a predetermined level.Hence, an image quality abnormality may be prevented from occurring dueto application of a modulated voltage to, e.g., the common electrode COMand pixel electrode PXL in the second driving period P2. Also possibleis it to prevent a significant image quality difference from the firstdriving period P1 when a non-modulated voltage is applied to, e.g., thecommon electrode COM.

Further, in some cases, the period of performing touch sensing withinone frame may be varied, preventing an image quality abnormality due toapplication of the modulated common voltage Vcom. As an example, in acase where each frame is divided into 20 periods, the modulated commonvoltage Vcom may be applied in the fourth, eighth, twelfth, andsixteenth periods of the first frame and in the fifth, ninth,thirteenth, and seventeenth periods of the second frame. In other words,the image quality abnormality (e.g., horizontal dimming) which occursonly in fixed areas may be dispersed and mitigated by varying, overtime, the area where display driving is performed in the period duringwhich the modulated common voltage Vcom is applied.

FIG. 8 is a view illustrating an example difference between commonvoltage Vcom and data voltage Vdata, caused by signals applied to acommon electrode COM during a period when touch sensing is performed anda period when touch sensing is not performed in a display device 100according to various aspects of the disclosure. FIG. 9 is a viewillustrating an example in which image quality is enhanced when a signalis applied to a common electrode COM according to the examples shown inFIGS. 6 to 8.

Referring to FIG. 8, a non-modulated common voltage Vcom is applied tothe common electrode COM in a first driving period P1. In the firstdriving period P1, the first voltage level L1 of the common voltage Vcomapplied to the common electrode COM may be, e.g., 4.56V.

In a second driving period P2, a touch driving signal TDS modulatedbased on a pulse width modulation signal PWM is applied to the commonelectrode COM. The touch driving signal TDS may be a pulse signal withthe second voltage level L2 and the third voltage level L3. As anexample, the second voltage level L2 may be 4.60V, and the third voltagelevel L3 may be 5.60V.

In other words, FIG. 8 illustrates an example in which the first voltagelevel L1 of the common voltage Vcom applied to the common electrode COMin the first driving period P1 is lower than the second voltage level L2of the touch driving signal TDS applied to the common electrode COM inthe second driving period P2.

The RMS value of the differences between the data voltage Vdata appliedto the pixel electrode PXL and the common voltage Vcom applied to thecommon electrode COM in the first driving period P1 and second drivingperiod P2 may be rendered to be even by setting the first voltage levelL1 to be lower than the second voltage level L2 of the touch drivingsignal TDS applied to the common electrode COM in the second drivingperiod P2.

The RMS value of the differences between the common voltage Vcom anddata voltage Vdata in the first driving period P1 and the RMS value ofthe differences between the common voltage Vcom and data voltage Vdatain the second driving period P2 may be adjusted to a predetermined levelby allowing the difference between the common voltage Vcom and datavoltage Vdata in the first driving period P1 and second driving periodP2 to be varied.

In other words, since the common voltage Vcom is 4.56V in the firstdriving period P1 and, in the second driving period P2, the low level ofthe common voltage Vcom is 4.60V, the difference between the commonvoltage Vcom and data voltage Vdata may not be identical although thesame level of data voltage Vdata is supplied in the first driving periodP1 and second driving period P2.

As an example, the difference between the common voltage Vcom and datavoltage Vdata in the second driving period P2 may be 0.04V larger thanthe difference between the common voltage Vcom and data voltage Vdata nthe first driving period P1. This involves an example in which the datavoltage Vdata is subtracted from the common voltage Vcom. In some cases,the difference between the common voltage Vcom and data voltage Vdata inthe second driving period P2 may also be regarded as being 0.04V smallerthan in the first driving period P1.

As such, although the difference between the common voltage Vcom anddata voltage Vdata is varied, the RMS value of the differences betweenthe common voltage Vcom and data voltage Vdata may be allowed to fallwithin a predetermined range by setting different levels for the voltageapplied to the common electrode COM in the first driving period P1 andsecond driving period P2, thereby preventing an image qualityabnormality from occurring in the period during which the modulatedcommon voltage Vcom is applied.

Thus, even when there are a period during which a modulated signal isapplied to the common electrode COM and a period during which anon-modulated signal is applied to the common electrode COM as shown inFIG. 9, it may be possible to prevent an image quality abnormality inthe period during which the modulated signal is applied or a differencein image quality from that in the period during which the non-modulatedsignal is applied.

FIG. 10 is a view illustrating an example configuration of a powercircuit and a touch driving circuit 150 for outputting signals to acommon electrode COM in a display device 100 according to variousaspects of the disclosure.

Referring to FIG. 10, a touch driving circuit 150 for driving a commonelectrode COM disposed on a display panel 110 may include an electrodedriver 151 and a sensing signal converter 152.

The electrode driver 151 may output a non-modulated common voltage Vcomor a modulated touch driving signal TDS to the common electrode COMunder the control of the touch controller 160. Upon outputting the touchdriving signal TDS to the common electrode COM, the electrode driver 151may receive a touch sensing signal TSS from the common electrode COM.

Upon receiving the touch sensing signal TSS from the touch drivingsignal (TDS)-applied common electrode COM, the sensing signal converter152 may convert the touch sensing signal TSS into digital sensing dataand transmit the digital sensing data to the touch controller 160.

The electrode driver 151 may output the voltage from a first powercircuit 200 or second power circuit 300 to the common electrode COM.

The first power circuit 200 may generate and output a first voltage V1with a first voltage level L1. The first power circuit 200 may be apower circuit included in the display device 100 to generate variousvoltages for display driving.

The first voltage V1 generated from the first power circuit 200 may betransferred to the second power circuit 300.

The second power circuit 300 may generate and output a second voltage V2with a second voltage level L2 and a third voltage V3 with a thirdvoltage level L3. The second voltage level L2 and the third voltagelevel L3 may differ from the first voltage level L1 as described above.

The second power circuit 300 may include a multiplexer 310. Themultiplexer 310 may be controlled by a touch sync signal Tsync outputfrom the touch controller 160 and may receive a pulse width modulationsignal PWM.

For example, the multiplexer 310 of the second power circuit 300 mayoutput a first voltage V1, which is received from the first powercircuit 200 in a period during which the touch sync signal Tsync is at ahigh level, to the electrode driver 151 of the touch driving circuit150.

The multiplexer 310 of the second power circuit 300 may output a secondvoltage V2 and third voltage V3, which are generated from the secondpower circuit 300 in a period during which the touch sync signal Tsyncis at a low level, to the electrode driver 151 of the touch drivingcircuit 150 based on the pulse width modulation signal PWM.

Thus, the electrode driver 151 of the touch driving circuit 150 mayoutput the first voltage V1 from the second power circuit 300 to thecommon electrode COM or a pulse signal of the second voltage V2 andthird voltage V3 to the common electrode COM.

An image quality abnormality may be prevented from occurring due toapplication of the modulated common voltage Vcom to the common electrodeCOM by setting the first voltage V1, second voltage V2, and thirdvoltage V3 so that the RMS value of the differences between the commonvoltage Vcom applied to the common electrode COM and the data voltageVdata applied to the pixel electrode PXL falls within a predeterminedrange.

The above description has been presented to enable any person skilled inthe art to make and use the technical idea of the disclosure, and hasbeen provided in the context of a particular application and itsrequirements. Various modifications, additions and substitutions to thedescribed aspects will be readily apparent to those skilled in the art,and the general principles defined herein may be applied to otheraspects and applications without departing from the spirit and scope ofthe disclosure. The above description and the accompanying drawingsprovide an example of the technical idea of the disclosure forillustrative purposes only. That is, the disclosed aspects are intendedto illustrate the scope of the technical idea of the disclosure. Thus,the scope of the disclosure is not limited to the aspects shown, but isto be accorded the widest scope consistent with the claims. The scope ofprotection of the disclosure should be construed based on the followingclaims, and all technical ideas within the scope of equivalents thereofshould be construed as being included within the scope of thedisclosure.

What is claimed is:
 1. A display device, comprising: a plurality ofpixels; a plurality of data lines electrically connected with theplurality of pixels; a plurality of touch electrodes overlapping atleast a part of the plurality of pixels; a first circuit configured tooutput a data signal to the plurality of data lines; and a secondcircuit configured to output a first signal having a first voltage levelto at least one touch electrode among the plurality of touch electrodesduring a first period, and a second signal alternating between a secondvoltage level and a third voltage level to the at least one touchelectrode during a second period, wherein the data signal includes analternating signal corresponding to the second signal during the secondperiod.
 2. The display device of claim 1, wherein the third voltagelevel is greater than the first voltage level.
 3. The display device ofclaim 1, wherein the first voltage level is between the second voltagelevel and the third voltage level.
 4. The display device of claim 1,wherein the second voltage level is between the first voltage level andthe third voltage level.
 5. The display device of claim 1, wherein thefirst period is a period for sensing a pen, and the second period is aperiod for sensing a finger.
 6. The display device of claim 1, whereinthe data signal is supplied to the plurality of data lines during thefirst period and the second period.
 7. The display device of claim 1,wherein a level of a signal supplied to the at least one touch electrodeis changed at a point between the first period and the second period. 8.The display device of claim 1, wherein a difference between a root meansquare (RMS) value of differences between the first signal and the datasignal applied during the first period and an RMS value of differencesbetween the second signal and the data signal applied during the secondperiod falls within a preset range when a grayscale represented by adata signal applied in the first period is identical to a grayscalerepresented by a data signal applied during the second period.
 9. Thedisplay device of claim 1, further comprising: a first power circuitconfigured to output a first voltage having the first voltage level; anda second power circuit configured to output a second voltage having thesecond voltage level and a third voltage having the third voltage level,wherein the second power circuit is configured to output the firstvoltage from the first power circuit to the second circuit or output amodulated signal having the second voltage and the third voltage to thesecond circuit.
 10. The display device of claim 1, wherein the secondcircuit is configured to receive a sensing signal from at least onetouch electrode during the second period.
 11. A touch circuit,comprising: a first circuit configured to output a data signal to theplurality of data lines; and a second circuit configured to output afirst signal having a first voltage level to at least one touchelectrode among a plurality of touch electrodes during a first period,and a second signal alternating between a second voltage level and athird voltage level to the at least one touch electrode during a secondperiod, wherein the data signal includes an alternating signalcorresponding to the second signal during the second period, and anelectrode driver configured to output a first signal having a firstvoltage level to at least one touch electrode of a plurality of touchelectrodes disposed on a panel during a first period, and a secondsignal alternating between a second voltage level and a third voltagelevel to the at least one touch electrode during a second period. 12.The touch circuit of claim 11, wherein the third voltage level isgreater than the first voltage level.
 13. The touch circuit of claim 11,wherein the first voltage level is between the second voltage level andthe third voltage level.
 14. The touch circuit of claim 11, wherein thesecond voltage level is between the first voltage level and the thirdvoltage level.
 15. The touch circuit of claim 11, further comprising: afirst power circuit configured to output a first voltage having thefirst voltage level; and a second power circuit configured to output asecond voltage having the second voltage level and a third voltagehaving the third voltage level.
 16. The touch circuit of claim 15,wherein the second power circuit is configured to output the firstvoltage supplied from the first power circuit to the second circuit oroutput a modulated signal having the second voltage and the thirdvoltage to the second circuit.